Two of the solar domestic hot water systems (SDHW) were assessed “very good” as the overall mark (system H3 and H11). With regard to the assessment of the thermal performance in total four SDHW systems obtained “very good” (system H3, H11, H13, H14). Two of these systems were equipped with flat plate collectors and two with vacuum tube collectors. This result shows that it is not necessary to use vacuum tube collectors in order to be assessed as “very good”.

Only for one system (H6) the thermal performance — and therefore also the overall mark — was rated with “fair”. The reasons for the relatively low thermal performance of this system were related to performance deficits of the solar collector and a disadvantageous control strategy. It is by chance that this system shows with 100 litres usable hot water volume also the lowest value in this category. Due to the assessment scheme used (see chapter 3.1) this fact is not the reason that the thermal performance of this system was only reacted with “fair”.

The solar combisystems C7 and C11 received „very good“ as the overall mark. In addition to these two systems, also system C5 shows a „very good“ thermal performance. It is encouraging that also in this category only one system (C9) was marked with „fair“. In this case the reason is predominantly related to a store concept that is designed disadvantageously with regard to thermodynamic aspects.